Method of preparing a lead carbonate product



- Feb. 21, 1933. s s, SVENDSEN 1,898,405

METHOD OF PREPARING A LEAD CARBONATE PRODUCT Filed Sept. 12, 1928 Jfzvenfm? Patented Feb. 21, 1933 UNITED STATES PATENT OFFICE SVEND S. SVENDSEN, OF CHICAGO, ILLINOIS, ASSIGNCR 0F ONE-HALF TO GEORGE BIBKENSTEIN METHOD OF PREPARING A LEAD CARBONATE PRODUCT Application filed September 12, 1928. Serial No. 305,596. g p

This invention relates'to the production of lead products from waste material and particularly from scrap storage battery plates.

L; In accordance with the present invention, such plates are placed in a rotating drum which may suitably be of iron, together with aqueous solution of alkali metal carbonates and, preferably, a small amount of a soluble 1o salt or acid which exerts a solvent effect upon lead compounds. The drum is rotated, whereby the plates are tumbled or caused to fall upon each other in the liquid menstruum, thereby detaching and pulverizing the filling,

15 which, in the plates employed, is substantially lead sulfate and peroxide from the grid. During this treatment, the solution is preferably heatedto increase the speed of the reaction between the alkali metal carbonate and the lead sulfate, whereby the latter is converted into lead carbonate. This heating may suitably be effected by steam introduced through a hollow trunnion with which the drum is provided.

bonates, of the alkali metals, in which term I expressly include ammonium, may be employed, I prefer to use sodium carbonate on account of its cheapness and effectiveness.

As the lead solvent compound, I prefer to employ acetic acid, acetates or nitrates. The effect of these substances. is catalytic, in that they bring lead compounds into solution as lead acetate, or lead nitrate, from which the lead is immediately precipitated by the carbonate present. The soluble acetates or nitrates are thereby regenerated and. react again with lead compounds in the same manner. This action is repeated again and again during the progress of the treatment The employment of the catalytic lead solvent speeds up the reaction considerably and enables the same to be completed under conditions under which it would otherwise be incomplete or would take an excessive period of time. I r

I have found that very considerable merit results from the employment of the plates,

Although any of the carbonates, or bicar- 't 'd l bl In me am or so u e .ihg. A temperature of about the boiling without balls or bars of otherhard material, for the purpose of breaking'up the filling of the plates and detaching it therefrom. Where other materials, such as steel balls or the like, are employed, the action is found to be excessive in that parts of the metal grids are broken up into finely dividedrstate so that the lead products derived from the filling are contaminated with grid metal. Since the grids contain substantial quantities of antimony the final result is that the employment of balls, bars and the like gives lead products derived from the filling of the plates, substantially contaminated with antimony. 65 On the other hand, when plates alone are employed in the rotating drum, together with the reaction solution, the collisions which effect the removal of the filling are of a different character, due to the comparative softness 0 of the plate and also due to the presence of the liquid menstruum. The result is that by the present process, the sulfate filling of the grids is atone operation separated therefrom, pulverized and the lead sulfate sub- 75 stantially completely converted into lead carbonate, yielding a mixture of lead carbonate and peroxide substantially uncontaminated with antimony. 1 1

The treatment may be effected at any temerature but is greatly accelerated by heatpoint of water is suitable and the mixture in the rotating drum may suitably be brought to that temperature by means of injected steam. I

r The accompanying drawing shows diagrammatically a suitable apparatus for carrying this method into eifect.

Figure 1 is a longitudinal section of the apparatus, and Y Y Fig. 2 is a transverse section on the line 22 of Fig.1.

Referring to the drawing, the apparatus comprises a drum 10 mounted bymeans of 5 trunnionsll and 12 on suitable bearings 13. The trunnion 12 may suitably be provided with a pinion 14: whereby the drum may be rotated. The trunnions 11 and 12 are preferably hollow and through the former passes o0 a stationary pipe 15 by means of which steam is supplied into the liquid in the drum. The drum is provided with a door 16 for the introduction of reaction materials and the withdrawal of the products of the reaction and is provided interiorly with longitudinal ribs 17 for the purpose of carrying the plates up to a suitable height from which they are dropped. vided with insulation 18, preventing loss of heat.

The invention will more readily be understood from the following description of a specific example thereof.

A ton of storage battery plates is placed in the revolving drum 10 and one hundred and sixty pounds of soda ash, eight pounds of sodium acetate and fifty gallons of boiling hot water are added. The door 17 is closed and the drum is rotated for about an hour low pressur steam being introduced during the process in order to raise the temperature of the menstruum to about the boiling point and maintain it at that temperature. During this operation, tl e filling material is substantially completely removed from the grids, thoroughly pulverized and the lead sulfate substantially completely converted into lead carbonate. The solution is decanted oif from the solid material which is washed several times with water, each addition of washing water being decanted off after settling. By this method the filling of the plates is converted into a pulverized mixture of lead carbonate and lead peroxide containing a small amount of spongy lead. This powdered material is separated from the grids and lugs by agitating with water and decanting the pulverized material with the water. This pulverized mixture is collected and dried in a centrifuge and may suitably be converted into litharge or red lead, in the known manner, by heating in a suitable roasting furnace to the appropriate temperature.

The grids contain a greater proportion of antimony than do the lugs. The lugs are, therefore, separated from the grid metal and both are melted separately.

Although the present invention has been described in connection with the details of the specific embodiment it must be understood that such details are not intended to be limitative of the invention, except in so far as included in the accompanying claims.

I claim:

1. The method of treating storage battery plates to remove the filling of the plates and to convert the lead sulfate of the filling into lead carbonate which consists in tumbling said plates upon each other in a solution of an alkali metal carbonate.

2. The method of disintegrating storage battery plates to recover the grid and lugs thereof and the filling in the form of a pulverized mixture consisting mainly of lead for the purpose of The outside of the drum is procarbonate and lead peroxide, which consists in tumbling such plates in a rotary drum together with an aqueous solution of alkali carbonate and separating the pulverized mixture from the metal parts.

3. The method of treating storage battery plates to remove the filling of the plates and to convert the lead sulfate of the filling into lead carbonate substantially uncontaminated with antimony which consists in tumbling said plates one upon each other together with a solution of an alkali metal carbonate and a minor proportion of a soluble lead solvent compound.

4. The method of disintegrating storage battery plates to recover the grid and lugs thereof and the filling in the form of a pulverized mixture consisting mainly of lead carbonate and lead peroxide which consists 'n tumbling said plates in a rotary drum together with an aqueous solution of alkali carbonate and a minor proportion of a lead solvent compound and separating the pulverized mixture from the metal parts.

The method mixture of lead carbonate and lead peroxide from the filling of storage battery plates without substantially breaking up the metallic part of the plate into small particles which consists in supplying said plates together with a substantial quantity of soda ash, a relatively small amount of sodium acetate and a substantial quantity of hot water to a rotary drum, maintaining the reaction mixture at a high temperature and rotating the drum.

In testimony whereof I have hereunto set my hand and seal this 30th day of August,

. SVEND S. SVENDSEN.

of producing a pulverized 

